1. Field of the Invention
Embodiments of the invention are related to retrieving an assembly from a wellbore. Embodiments of the invention are also related to the practice of sidetrack drilling for hydrocarbons using the assembly. The assembly may include a whipstock, a latch, and an anchor.
2. Description of the Related Art
Technology has been developed to allow an operator to drill a primarily vertical well and then drill an angled lateral borehole off of the vertical well. Generally, the vertical wellbore is first drilled and then reinforced with casing strings. The strings of casing are cemented into the wellbore. Cement is injected down the wellbore into the annular regions between the strings of casing and the surrounding formation. The combination of cement and casing strengthens the wellbore within the formation for the production of hydrocarbons.
It may be desirable to drill a lateral wellbore into production zones surrounding the formation by utilizing the casing of the vertical wellbore. In one instance, a tool known as a whipstock is positioned in the casing at a particular depth, such as above one or more producing zones. The whipstock is designed to direct a drilling operation into a side of the casing by deflecting a drill bit against the whipstock into the casing wall to create a window. After the window is created, the drill bit may be further run into the vertical well and urged through the window to form a new lateral wellbore in the desired direction. This process is sometimes referred to as sidetrack drilling.
Prior to forming the window and the lateral wellbore, an anchor is first set in the vertical wellbore at the desired depth. The anchor may act as a fixed body against which other downhole tools may be engaged to activate different tool operations. The anchor typically may be oriented in the desired direction of the lateral wellbore.
A whipstock is subsequently run into the wellbore and operatively connected to the anchor. The whipstock generally includes a deflection portion having a concave face. The deflection portion receives and directs the drill bit as it is urged downhole into the side of the casing. In this way, the window and lateral borehole may be formed at the desired depth and in the desired direction.
Once the lateral wellbore has been formed, traditionally, the sidetracking arrangement is set up to be retrieved in two trips. The first trip is made to retrieve the concave. A second trip is then made to retrieve the anchor, if the anchor is retrievable. The subsequent trips into and out of the wellbore increase the amount of time, and thus cost, to complete a sidetrack drilling operation. Some arrangements, however, utilize a permanent anchor that is left in the vertical wellbore and drilled through if necessary. Yet, if a second lateral wellbore is to be formed above or below the permanent anchor, the use of a second anchor is required.
Therefore, there is a need for an-assembly that can be used to reduce the number of trips necessary complete a wellbore operation, such as a sidetrack drilling operation. There is also a need for an improved method and apparatus for retrieving an assembly from a wellbore.